This invention relates to a cathode ray display tube having an envelope with a glass faceplate, a screen carried on the inner surface of the faceplate comprising phosphor material and a screen electrode, an electron multiplier disposed adjacent the screen with its output facing the screen, and termination means for establishing electrical connection with the screen electrode and an electron multiplier electrode from outside the envelope.
The invention is concerned especially, but not exclusively, with a so-called "flat" cathode ray display tube generally of the kind described in published British Patent Application No. 2101396A corresponding to U.S. patent application Ser. No. 830,388, filed Feb. 14, 1986. With this kind of display tube a low energy electron beam is directed along a path parallel to screen and is turned through 180.degree. so that it travels in the opposite direction. The beam is subsequently deflected onto the input surface of the electron multiplier where it undergoes electron multiplication, the current multiplied beam then being accelerated by the field established between the multiplier and the screen electrode onto the screen to excite the phosphor material. In one realised version of this display tube, although not specifically described in the aforementioned specification, the electron multiplier comprises a glass microchannel plate multiplier having electrodes on its input and output surfaces. Electrical interconnection from outside the envelope with the screen electrode, which comprises an aluminium layer deposited over the phosphor material, and the output surface electrode of the electron multiplier has been achieved by means of insulated wires extending through lead-in sleeves sealed in the envelope wall adjacent the faceplate which are connected to contact areas of the electrodes.
Whilst such connections were found to perform satisfactorily electrically, difficulty was experienced in ensuring adequate vacuum-tight seals between the wires and the envelope wall. More importantly however, the connections occupy a relatively large volume. Since a major object of a flat display tube is to minimise volume, the amount of space available within the envelope is at a premium and with internal components being located close together, the connections can interfere with other components, especially during assembly of the display tube. Any reduction in the volume occupied by internal components is considered therefore beneficial.
It is an object of the present invention therefore to provide a form of terminal arrangement providing interconnection between the screen and multiplier electrodes and outside the envelope which occupies little volume whilst at the same time maintaining reliable performance.